Composting Toilet Plans

The following plans will help you build a composting toilet that is odorless, incredibly easy to use, fully-functional, and portable. That last point is probably one of the most common reasons why people build a composting toilet in the first place; they're looking for an inexpensive way to dispose of human excrement in a remote location (e.g. cottage or cabin).

Before You Begin Building...

Before you start tackling these composting toilet plans, we want to give you a heads up about a few things.

First, in order to use this composting toilet properly, you're going to need an outdoor composting bin system. We're going to go into more details about this system on the following pages, however, we wanted to introduce the topic early on in these plans.

Second, these composting toilet plans call for the use of cover materials. Cover materials are just that, they are the materials you will use to cover your waste once you have used your toilet. A variety of materials can be used for cover, including sawdust, peat moss, cured compost, leaf mold, and/or rice husks.

An ideal cover material is highly biologically active (i.e. high in microbial activity). The more active this material, the better it will be at absorbing odors from your compost toilet. Please note that we do not recommend sawdust from woodworking shops, since this material is completely dry and devoid of biological activity. Instead, when we say sawdust, we are referring to the waste product from sawmills. This type of saw dust is still moist, rich in microbes, and partially decomposed; all of which make it a great cover material.

What You'll Need

To successfully use these composting toilet plans, you will need the following materials:

Source of cover material (see important notes above)

4 identical 5-gallon buckets

1 18"x18" piece of 3/4" AC fir plywood

1 18"x3" piece of 3/4" AC fir plywood

2 10"x18" pieces of 3/4" AC fir plywood

2 10"x19.5" pieces of 3/4" AC fir plywood

4 3"x12" piece of 3/4" AC fir plywood

2 metal hinges

1 standard toilet seat

Jigsaw

Drill

30+ 1-1/2 screws

Wood glue

What is AC fir plywood?

Softwood comes in a variety of grades (A through D). Each side of the wood is graded according to the number and severity of knots, splits, and other defects. Grade A is the best, whereas Grade D is the worst. So in this instance we are recommending one side of the plywood be Grade A (the fir side), and the other side be Grade C. This is one of the most common grades of fir plywood, so you shouldn't have a problem finding it.

Instructions

Step 1

Assemble the frame of your toilet. The finished frame will be 21" long, 18" wide, and 10" deep. Begin by attaching the two 10"x18" pieces of plywood to the two 10"x19.5" pieces of plywood, using screws and wood glue. Be sure the 10"x19.5" pieces fit inside the other two pieces for a total length of 21". Also, be sure the fir side of the plywood is facing out.

Step 2

With the frame in the upright position, place the 18"x3" piece of plywood on top, and line it up with one end of the frame. Again, be sure the fir side of the plywood is facing out. Now attach this 18"x3" piece of plywood using screws and wood glue.

Step 3

Place the 18"x18" piece of plywood on top of the frame in front of the 18"x3" piece you just secured. These pieces will eventually be attached together using the hinges, however, you must first cut out the hole for the bucket. Be sure the fir side of the plywood is facing out.

Position the bucket 1.5" from the front edge of the box, and center it from both sides. Draw a circle around the bucket's edge to indicate where you will be cutting it. Remove the bucket, and use the jigsaw to cut the hole for the top of the bucket.

Step 4

Now that the hole has been cut, reposition the 18"x18" piece of plywood on top of the frame. Using eight screws and the two hinges, connect the 18"x18" piece of plywood with the 18"x3" piece. Be sure to position these hinges close to the edges of the toilet, so that they don't interfere with the toilet seat.

Step 5

You will now attach the legs (four 3"x12" pieces of plywood) to each corner of the underside of the frame. It is very important to adjust the length of these legs, so that the top of the compost toilet is positioned 1/2" below the top of the bucket. The bucket should protrude through the top of the toilet by 1/2". This will ensure a tight-fit, and prevent any waste from missing the target. This is especially important if children will be using your compost toilet.

Step 6

The next step in these composting toilet plans is to attach the toilet seat. Before doing so, you will need to reposition the bumpers that are found on the underside of the seat. Typically, these bumpers point inwards, but this will interfere with the bucket, you so have to swivel them sideways (almost parallel to the toilet seat edge).

Position the toilet seat over the bucket, and mark where you will need to drill holes to attach it to the frame. Drill these holes, and attach the toilet seat.

Step 7

Your new compost toilet is now ready to use. Although, to make it's appearance a little less rustic, you may want to stain, varnish, or paint it. Notice how well Jame's compost toilet matches his bathrooms decor in the image below.

ATTENTION - The toilet is only one part of a larger three part composting system. This system will NOT work without all three parts in place. To learn more about the other parts, including the proper maintenance of your toilet, and how to properly compost your waste, please refer to page two of these composting toilet plans. It is incredibly important that you understand this entire system, so that you eliminate all pathogens.

The previous composting toilet plans were adopted from Joseph Jenkin's incredible book The Humanure Handbook. If you have any interest in learning more about this subject, we highly recommend reading his book (it's free online).